1. Field of the Invention
This invention relates to a resin composition and packaging materials for photosensitive materials such as photographic photosensitive materials.
2. Description of the Prior Art
Resin compositions for packaging materials for photographic photosensitive materials are disclosed in Japanese Patent KOKAI Nos. 63-217548 and 1-243050 and the like, resin compositions for films for photographic photosensitive materials are dislclosed in Japanese Patent KOKAI No. 58-132555, and spools for a photographic film are disclosed in U.S. Pat. No. 4,796,823. In the above materials, the light-shielding ability was secured by blending a light-shielding material such as carbon black. Then, heretofore, when the light-shielding ability of the films for photographic photosensitive materials was raised, the blending amount of the light-shielding material was increased. However, the increase in the amount of the light-shielding material resulted in an increase in the occurrence of lumps and fish eyes and degradation of physical strength, moldability, heat sealing properties and the like. While, since the size and form of the spool for a photographic film are stipulated by JIS, a great quantity of a light-shielding material was blended in order to secure light-shielding ability at thin portions. As a result, the quantity of the light-shielding material at thick portions was too high.
Incidentally, as to the materials which lose their value upon exposure to light, such as photographic photosensitive materials, packaging materials capable of complete shielding from light are used. The packaging materials have various important properties such as resistance to the occurrence of pinholes, sealability, moistureproofness, gas barrier, sufficient physical strength and antistatic ability capable of preventing spark discharge as well as the above light-shielding ability.
As conventional packaging materials, there were a packaging material composed of an aluminum foil on both sides of which flexible sheet(s) or LDPE resin film(s) containing carbon black were laminated, and a packaging material laminated with a light-shielding film containing more than 1 wt. % of a light-shielding material and more than 50 wt. % of L-LDPE resin. An example is shown in FIG. 19 which consisted of a polyethylene resin film 21a containing a light-shielding material and an aluminum vacuum-metallized biaxially stretched nylon resin film 22 composed of a biaxially stretched nylon resin film 23 provided with an aluminum vacuum deposited membrane 19 laminated thereto through an adhesive layer 2. However, when-they were used for packaging a roll or sheets of a heavy photographic photosensitive material having sharp edges, pinholes or elongation occurred by the sharp edges. Therefore, in order to secure light-shielding, the packaging bag was made as a double-sheet bag and was accordingly expensive. Another packaging material was composed of an aluminum foil and two light-shielding L-LDPE resin films laminated on both sides of the aluminum foil (Japanese Patent KOKAI No. 60-189438). The packaging material was also used as a double-sheet bag in order to secure the qualities of the packaged materials. The inventor disclosed a packaging material having a double layer-coextruded film such as composed of a L-LDPE resin film and a polypropylene resin film as a packaging material capable of securing the qualities even as a single-sheet bag (U.S. Pat. No. 4,780,357). An example of the packaging material is shown in FIG. 20 which consisted of a light-shielding coextruded double layer film 24a consisting of a HDPE resin film 25a containing a light-shielding material and a L-LDPE resin film 26a containing a light-shielding material and an aluminum vacuum-metallized biaxially stretched nylon resin film 22 laminated thereto through an adhesive layer 2. However, in the case of the above packaging material, light-shielding and moistureproofness could not be secured by the shaking or shock during exportation or long transportation, by rough handling of freight such as by dropping or by being thrown out in courier or air cargo, by the increase of impact force by the space in a carton box or corrugated board box, or the like. That is, in the case that the packaged material was sheets, pinholes and thinning of light-shielding layers occurred by the sharp edges or corners, and in the case that the packaged material was a roll, breakage, pinholes or abrasion occurred by the sharp edges of the roll or the corners of the core.